Things can change and break. 

Damage happens when things change. 
Small parts inside things can shift. This can make cracks. 
Fire and water can cause damage. 
Living things can get hurt. We call this an injury.
People can fix many things. We can make them work again.
Damage is a change in a thing. It makes an object work less well. It can even make it break. 
All physical damage starts at a tiny level. It happens to atomic bonds. These are the tiny links that hold atoms together. If these bonds shift or break, the object changes. Some materials have elasticity. This means they can bounce back after a change. Other materials have plasticity. This means the changes are permanent. This can lead to cracks or faults. 
Many things can cause damage. Fire and water can hurt objects. Even bugs can damage cabbage leaves. Some damage is accidental. Other damage is done on purpose.
Living things can also experience damage. We often call this an injury. Damage can happen to tiny parts like DNA. It can also hurt larger parts like the brain. Large scale damage to the body is called trauma. As living things age, they may lose the ability to heal quickly.
Damage is any change that makes a thing work less well. It moves an object away from its original state. This change might not break a system completely. Instead, it might just stop the system from working perfectly. 

Physical damage starts at a tiny level with atoms. Atoms are held together by bonds. Damage happens when these atomic bonds shift or break. The way a material reacts depends on its elasticity. Elastic materials can bounce back from a change. Other materials have plasticity. This means the changes are permanent. Plasticity can lead to cracks or faults in the material. These small changes eventually show up in the big world. They can look like cracks or bent shapes.
Many different forces can cause damage to objects. Fire can cause damage through burning. Water can hurt materials that do not resist it. Radiation can also cause harm. Some machines have special kinds of damage. For example, hydrogen can damage certain metals. Other objects suffer from foreign object damage. This happens when debris or strange items get inside. 
Living things also experience damage, which we call injury. This can happen to very small parts like DNA. It can also affect larger parts like the brain or nerves. Large damage to the body is often called trauma. As living things age, they may find it harder to heal. Some scientists think damage is one reason why we age. The other reason might be a biological timetable. Internal and environmental assaults can cause this damage to build up over time.
Damage can also happen to things we cannot touch. We can talk about damage to a reputation or a relationship. Even the value of a business can go down. In law, money paid to fix a loss is called damages. This money helps people after an injury or loss. Damage can even happen to big groups like governments. For example, vandalism can damage public buildings. This shows how damage affects almost everything in our world.
Damage is defined as any change that degrades a thing from its initial state. It is a change introduced into a system that adversely affects its current or future performance. This does not always mean a system loses all functionality. Often, it simply means the system no longer operates in an optimal manner. 
All physical damage begins at the atomic level. It starts when atomic bonds shift or break. The rate of this damage depends on the elasticity of the bonds in the material. Elasticity describes how a material responds to stress. If a material is elastic, changes to its consistency are reversible. The material can bounce back from potential damage. However, if a material has plasticity, the changes are permanent. Each plastic change increases the chance of a crack or fault appearing. 
Damage manifests differently depending on the material. At the macroscopic level, we see cracks, deformation, or structural weakening. Some weakening is not even visible to the eye. Different forces cause different types of damage. Fire causes damage through burning. Water can damage materials that are not resistant to it. Ionizing radiation can cause radiation damage. Mechanical systems face unique challenges. Foreign object damage occurs when debris or strange substances enter a system. Metals can suffer hydrogen damage through interactions with hydrogen. Materials also face damage mechanics from cyclic mechanical loads.
Living organisms experience damage, which is often called an injury. This damage occurs at many different scales. It can be microscopic, such as DNA damage or damage to a biological cell. It can also affect larger systems like nerve damage, brain damage, or articular cartilage damage. Large-scale damage to the body is often called trauma. 
Damage also applies to intangible things that we cannot touch. We can describe the degradation of a reputation, a relationship, or self-image. Even goodwill or the value of an idea can be damaged. In the legal world, the term "damages" has a specific meaning. It refers to an award of money paid to a person. This money serves as compensation for a loss or an injury. This helps restore the person after economic or physical damage has occurred.
In a social context, we look at institutional damage. This can mean unintended consequences to an individual caused by an institution. This might happen to a hospital patient, a child in school, or a prisoner. Some forms, like medical errors, are easy to measure. Others, like damage to mental health, are much harder to measure. There is often controversy regarding whether this damage can be quantified. 
Conversely, damage can be done to the institutions themselves. For example, the suspension of political rights can damage democratic institutions. Vandalism of public buildings is another example. Large epidemics can also disrupt the normal functioning of society's institutions. Even external military intervention or the "resource curse" can cause institutional damage. Sometimes, damage happens in both directions. During the 1940s, the House Committee on Un-American Activities caused damage to individuals. At the same time, it damaged the political institutions of individual rights and freedom in the United States.
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